This material is based on work supported by the National Institute of Food and Agriculture, under award number 2014-51181-22382. Any opinions, findings, conclusions or recommendations expressed in this presentation are

those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

Douglas Hayes (PD), Annette Wszelaki, Jennifer DeBruyn, Markus Flury, Eric Belasco, Sean Schaeffer, Arnold Saxton, Susan Schexnayder, Margarita Velandia, Larry Wadsworth, Mark Fly, Carol Miles, Debra Inglis, Thomas Marsh, Jessica Goldberger, Suzette Galinato, Chris Benedict, Jeremy Cowan, Peter Tozer, Andy Bary, Lydia Tymon, Courtney Lyons, Jennifer Moore, Amy Salamone, Babette Gunderson, Ed Scheenstra, Jacky King, Marie English, Sreejata Bandopadhyay, Nurul Farhana Omar, Shuresh Ghimire, Henry Sintim, Kuan Chen

USDASCRIProjectNo.2014-51181-22382

www.biodegradablemulch.org

Biodegradable Plastic Mulch

Sociology Economics

MaterialScience

Overall Research Project

HorticulturePlant Pathology

Soil Ecology

Sociology Economics

MaterialScience

Overall Research Project

HorticulturePlant Pathology

Soil Ecology

Mount Vernon, Washington

Knoxville, Tennessee

Field Experiment

Field Experiment

Field Experiment

Field Experiment

Paper No mulch Polyethylene

BDM 2 BDM 1 BDM 3

BDM 4 BDM 5

Biodegradable Plastic

1.  Does biodegradable plastic affect soil health?

2.  Does biodegradable plastic degrade completely in soil?

3.  Are residues released during degradation?

Questions:

Soil Health Assessment

Aggregate Stability

−50

0

50

100

Chan

ge in

agg

. sta

bility

(%)

b

aa

aa

a a aa

a a a a

Knoxville,TN Mount Vernon, WA

No−mulchPaperBioAgri

NaturecycleOrganixPLA/PHA

Polyethylene

b ab

2015-2017

Soil Health Assessment

Microbial Communities

2015-2017

Tennessee Washington

Spring 2015

Spring 2015Spring 2017

Spring 2017

Fall 2015 Fall 2015

Fall 2017Fall 2017

Biodegradable Plastic Mulches

1.  Similar agronomic benefits2.  No short-term effects of mulches on soil health3.  Seasonal changes more pronounced than mulch effects4.  Soil health is a slow changing process

long-term study needed

Ramani Narayan (narayan@msu.edu)MSU University Distinguished Professor

Biodegradable Mulch Film Basics

If you use any of the slides/materials, please reference authorship and affiliation (Ramani Narayan, Michigan State University) – thank you -- Copyright Ramani Narayan

Narayan

QUESTIONS1. What is the effect on overall soil health, including soil biology, when this material

biodegrades

2. What is the cumulative effect of the continued use of this biodegradable biobased mulch film, on soil nutrient balance, soil biological life, and soil tilth, when used in the same area of the field for 3-5-10 years?

3. What effect does the breakdown of these polymers have on soil and plant life as well as livestock that would graze either crop residues or forages grown the subsequent year after this mulch film was used?

4. Are there different cropping systems, climate, soil types or other factors that affect the decomposition rate (Examples would be long cold winters, or exceptionally dry conditions, such as found in a desert)?

5. Are there metabolites of these mulches that do not fully decompose, and if so, is there an effect upon soil health or biological life?

6. Can you provide information on the existence or development of biobased biodegradable mulch films that would meet the requirements of NOP policy memorandum 15-1?

What does “Biodegradable” Mean?Can the microorganisms in the target disposal system (composting, soil, anaerobic digestor) assimilate/utilize the carbon substrate as food source completely and in a short defined time period?

Oligomers & polymer fragments

Hydrolytic

Polymer chains with susceptible linkages

EnzymaticOxidative

Environment – soil, compost, waste water plant, marine

STEP 1

Biodegradation(Step 2): Only if all fragmented residues consumed by microorganisms as a food & energy source as measured by evolved CO2 in defined time and disposal environment

CO2 + H2O + Cell biomass

Completemicrobial assimilaton

defined time frame, no residuesSTEP 2

Carbon footprint reduction strategy using bio content

Basics of microbial utilization -- biodegradability

4

Microorganisms utilize carbon substrates as “food” to extract chemical energy for their life processes.

They do so by transporting the C-substrate inside their cells and:

Under aerobic conditions, the carbon is biologically oxidized to CO2 releasing energy that is harnessed by the microorganisms for its life processes. Under anaerobic conditions, CO2+CH4 are produced.

Thus, a measure of the rate and amount of CO2 or CO2+CH4 evolved as a function of total carbon input to the process is a direct measure of the amount of carbon substrate being utilized by the microorganism (percent biodegradation)

Glucose/C-bioplastic + 6 O2 6 CO2 + 6 H2O; ∆G0’ = -686 kcal/mol

Glucose/C-bioplastic 2 lactate; ∆G0’ = -47 kcal/mol

CO2 + CH4

level of biodegradation needed to claim safe and efficacious removal of the plastic carbon from the environmental compartment

0

10

20

30

40

50

60

70

80

90

100

0 20 40 60 80 100 120 140 160 180 200

Time (days)

% C

con

vers

ion

to C

O2

(% b

iode

grad

atio

n)

lagphase

biodegradation phase

plateau phase

biodegradation degree

O2

Soil & Test

Materials

CO2

ASTM D5988; ISO 17556 -- Soil biodegradability test methodEN 17033 – soil biodegradability specifications for biodegradable mulch film

Unqualified use of the term “biodegradable” is wrong, misleading, and deceptive. It violates the law in the State of California and U.S. Federal Trade Commission (FTC) green guides & in Australia too

Need to define disposal environment, time/rate and extent of biodegradation – qualified biodegradability claim

Soil biodegradability (mulch films & ag products)

Compostable plastics -- enabler for food and organic waste diversion from landfills to composting

• Need complete microbial assimilation and removal from the environmental compartment in a short time period otherwise may have environmental and health consequences

• Degradable, partial biodegradable not acceptable – serious health and environmental consequences

• Phil. Trans. Royal. Soc. (Biology) July 27, 2009; 364

CAUTION!!!

Misleading (Green Washing) Claims -- Additive Technology

• “Plastic products with our additives at 1% levels will fully biodegrade in 9 months to 5 years wherever they are disposed like composting, or landfills under both aerobic and anaerobic conditions”

The 50% Bio-Batch film did not degrade as completely or as quickly as the cellulose. At the end of the test, 19% of the film had degraded.The results of the aerobic degradation tests indicate that, in time, plastics produced using Bio-Batch pellets will biodegrade in aerobic conditions.DATA DOES NOT SUPPORT THE CONCLUSIONS!

Narayan

MISUSE OF BIODEGRADABILITY CLAIMS• Chem. Commun., 2002, (23), 2884 - 2885

– A hypothesis was developed, and successfully tested, to greatly increase the rates of biodegradation of polyolefins, by anchoring minute quantities of glucose, sucrose or lactose, onto functionalized polystyrene (polystyrene-co-maleic anhydride copolymer) and measuring their rates of biodegradation, which were found to be significantly improved

• PRESS• Sugar turns plastics biodegradable. Bacteria make a meal of sweetened polythene

and polystyrene.

weight loss of only 2-12%,

Only sugar is being assimilated, PE chain intact – Is this a genuine example of biodegradable plastic?

Narayan

Aliphatic-aromatic copolyester

Copolyester

C C

O O

O CH2 O C

O

CH2 C

O

m nx y z

Terephthalic acid Diol Aliphatic diacid

Tm ~ 110 -125 0C

Completely Biodegradable (microbial assimilation) under composting conditions

BASFKingFaShowaMitsubishiNovamont

C-14 label on aromatic carbon – the most recalcitrant component

Narayan

Aliphatic-aromatic copolyester

Aromatic ring carbons, the most recalcitrant component is assimilated by the compost microorganisms as seen by evolution of the C-14 carbon dioxide

Narayan Zumstein et al., Sci. Adv. 2018;

“Carbon from each monomer unit of PBAT was used by soil microorganisms, including filamentous fungi, to gain energy and toform biomass”

Biomass refers to cellular biomass – PBAT carbons incorporated into lipid molecules

Narayan

BASICS -- TERMINOLOGY

Biobased plastics/products refers to the “beginning of life”

Origins of the carbon in the polymer

Plant-biomass feedstock (biobased) vs petro-fossil feedstock

H2C CH2nPE

C

O

O CH2 CH2 OC

O nPET

CHCH3

CO

O

PLAn

R' NN

H

C

O

O

H

C

O

R O

n

* O(CH2)x

O

O

(CH2)y

O

*

n

Biobased polyester

Biobased polyurethaneCellulose

WHY BIOBASED??

What are the benefits of replacing petro/fossil carbon with biocarbon?

Reduced carbon footprint Food security and creating value for rural agrarian economy Create “wealth” in rural agriculture through value-added industrial

products

CAUTION:Need to still address the issue of end-of-life

mechanical, chemical, biological/organic recycling

H2C CH2nPE

CHCH3

CO

O

PLAn

Understanding “BIOBASED & BIODEGRADABILITY” at Molecular level

BIO-PET

C

O

O CH2 CH2 OC

O nBiobased polyeter

HO

(CH2)xO

O

(CH2)y

O

OH

n

H2C CH

CH3 nPP

CH3

O

O

O O

OCH2

CH3

x y

PHBV -- poly(3-hydroxybutyrate-co-3-hydroxyvalerate) PHAs

Biobased Plastics are NOT necessarily biodegradable/compostable

Biodegradable-Compostable Plastics are NOT necessarily Biobased

Thank You

15